968 MISC. PUBLICATION 423, U. S. DEPT. OF AGRICULTURE 

 79. HEMIZONIA. Taeweed 



Annual herbs; leaves all or mostly alternate, pinnatifid to entire, 

 sometimes spinescent; heads small or medium-sized, radiate, yellow, 

 sometimes leafy-bracted ; phyllaries in a single series, each partly 

 enclosing a ray achene in its enfolded base; ray achenes much thick- 

 ened, epappose, tipped with a very short oblique beak; disk achenes 

 all or mostly sterile, epappose or with a pappus of several often 

 connate squamellae or paleae. 



Key to the species 



1. Leaves and their lobes with spinescent tips; heads involucrate by spinose- 

 tipped bracts; receptacle paleaceous throughout; disk achenes epappose. 



1. H. PUNGENS. 



1. Leaves and their lobes not spinescent-tipped; heads not involucrate; pales of 

 the receptacle in a single row, connate into a cup; disk achenes with 



pappUS 2. H. KELLOGGII. 



1. Hemizonia pungens (Hook, and Arn.) Torr. and Gray, Fl. North 



Amer. 2: 399. 1843. 



Hartmannia (?) pungens Hook, and Arn., Bot. Beechey Voy. 357. 



1840. 

 Centromadia pungens Greene, Man. Bot. San Francisco Bay 



196. 1894. 



Santa Cruz River bottoms, Tucson, Pima County (Thornber, 

 May 1903). California; a casual introduction in Arizona. This 

 collection was originally reported 93 as Hemizonia fitchii A. Gray. 



2. Hemizonia kelloggii Greene, Torrey Bot. Club Bui. 10: 41. 



April 1883. 



Hemizonia wrightii A. Gray, Amer. Acad. Arts and Sci. Proc. 19: 

 17. October 1883. 



"Common around habitations on mesas," Tucson, Pima County 

 (Thornber in 1903 [no. 386] and in 1905). California; introduced 

 in Arizona. 



Two of the three sheets examined are true H. kelloggii, with the 

 pappus squamellae partly united into a tube; the other (no. 386) 

 has the squamellae mostly free, and represents the form described as 

 H. wrightii A. Gray. 



80. LAYIA 



Plant low, annual, pubescent and stipitate-glandular ; leaves 

 lanceolate or linear, mostly alternate, the lower ones pinnatifid or 

 incised, the upper leaves entire; heads terminal, showy, the rays 

 white, the disk yellow; receptacle with a series of thin pales between 

 the rays and the outer disk flowers, otherwise naked; ray achenes 

 glabrous, epappose; disk achenes pubescent, their pappus of about 

 10 stout villous bristles, the hairs on their outer side straight, on the 

 inner entangled into a woolly mass. 



93 Thornber, J. J., in Spalding, V. M. distribution and movements of desert plants. Carnegie 

 Inst. Wash. Pub. 113: 112. 1909. 



